1. Field of the Present Invention
The present invention generally relates to devices and methods for storing and dispensing quantities of liquids. More specifically, the present invention uses a macro/micro interface and a micro electro mechanical system to store and dispense chemical and biological liquids in minute quantities.
2. Description of the Related Art
Until the relatively recent advent of combinatorial chemistry and genetic research spawned the need for high-throughput analyzing and screening techniques, researchers performed such assays using vials, tubes and beakers. However, with ever more substances available via synthesis or via combinatorial techniques for testing, the need has arisen to test the possible role of thousands, or even millions of substances, in comparable numbers of possible reactions. Miniaturization has been identified as a promising path to more efficient, e.g. less expensive, chemical, and in particular, drug, analysis and screening. Discussions of various aspects of such analysis and screening techniques are found in J. D. Devlin, ed., High Throughput Screening: The Discovery of Bioactive Substances (Marcel Dekker, Inc., New York, 1997); which is incorporated herein by reference to more fully describe the state of the art to which the present invention pertains.
A minaturization apparatus may be broadly classified into at least two categories. A first category deals with micro-chemistry and involves the placement of chemical substances in small amounts in sites formed on glass or a similar substance. These small amounts generally range between picoliter and microliter aliquots. Such amounts shorten reaction times significantly over those conducted in reaction vessels holding on the order a fraction of a milliliter, as currently achievable by a lab technician working “by hand”. In addition to microchemical testing, levels of gene expression and protein levels can be tested on a large scale using micro-chemistry.
An example of this first category is the development of microplate technology in which a substrate (e.g. plastic) may include site densities of up to about many thousand (e.g. 96 to about 10,000) sites. This technology generally includes the use of complex micro-robotics or the adaptation of ink-jet technology to apply chemical and biochemical substances to chosen sites on the substrates. Frequently, at least one of the reactants in a chemical assay to be performed is chemically linked to or otherwise immobilized at the reaction site, so that fluids may be added to and removed from the reaction site without removing an intermediate or end product of the reaction, since it is desirable that the intermediate or end product(s) is (are) to be retained at the reaction site, so that the outcome of the chemical assay may thereby be determined.
Currently, credit-card sized chips (e.g. glass chips) with greater than many thousand (e.g. 10,000) sites are in development (See Leach, 1997, Drug Discovery Today, 2:253). Each site may cover an area of 100 square microns and may contain much less than 1 microliter in volume. The chip is a glass sandwich formed from individual glass layers, which are glued together to form tubes to move substances between sites. The tubes are generally formed by cutting (e.g. etching), trenches or grooves in a first glass layer and then sandwiching the trenches under a second glass layer.
A second category of miniaturization apparatus (e.g. “lab on a chip”) employs silicon or glass as some functional modality in some functional (e.g. electrical or mechanical) modality as a substrate, and chemicals then are tested on the substrate. This category of apparatus may include the use of electrokinetic motive forces. Micro-robotics or microchemistry, or both, may be employed with such substrates, including the use of micro-fluidic pumps (pumps having no moving parts) to move substances between sites, the use of electrophoresis or electrokinetic pressure pumping (a combination of electrophoresis and electro-osmosis) as motive agents to analyze chemical reactions acting over the surface of the silicon substrate (for about e.g. 25 reaction sites).
Currently, to achieve high-throughput analyzing and screening techniques for chemical and biochemical reactions, complex operations using combinations of films and substrates or complex robotics for the precise placement of fluids carrying chemical compositions, or both are required. Such complex systems are subject to failure due to their inherent complexity and are expensive to manufacture and maintain.
Moreover, current methods and systems for liquid sample processing consume large amounts of expensive, toxic and specialty reagents. This is especially true in the pharmaceutical arts when throughput rates for a singe lab can be up to 100,000 samples per day, where each sample includes a volume on the order of 2-20 microliters.
Accordingly, it is desirable to be able to process hundreds or thousands of liquid samples concurrently at a volume in the pico to micro liter range.